Heart diseases refer to several classes of cardio and cardiovascular disorders and co-morbidities relating to the heart and blood vessels. Heart disease is often treated through a combination of medication and lifestyle modification. In severe cases, a monitoring or therapy delivery device, referred to as an implantable medical device (IMD), is surgically implanted to collect cardiac performance data and to deliver therapy to the heart, when needed. IMDs are also used to provide neural stimulation, dispense drugs, and other functions, as would be appreciated by one skilled in the art.
Periodically, data collected by an IMD can be downloaded for further analysis and, if required, new performance instructions can be uploaded to reprogram the IMD. Typically, an IMD communicates with a programmer or a dedicated repeater located outside the body in a data exchange session. To minimize patient risk, wireless telemetry, such as inductive telemetry, is normally used to non-invasively communicate with the IMD.
Although inductive telemetry requires little or no on-board energy to transmit information, inductive telemetry has a few shortcomings. First, inductive telemetry is short range, typically about six centimeters, and requires close proximity between a patient and the programmer or repeater. The patient's movements are limited while data transfer is ongoing. In addition, inductive telemetry has a slow data transfer rate, which is directly proportional to the carrier signal frequency. Only low frequency signals can be used as carrier signals due to the low-pass filtering effect of the metal casing of the IMD, resulting in a transmission speed of several kilobits per second. This transfer rate is inadequate for modern IMDs, which normally can contain millions of bits of patient physiological data.
Recently, radio frequency (RF) telemetry, a form of long range telemetry, has emerged as a viable alternative to inductive telemetry, such as described in commonly-assigned U.S. Pat. No. 6,456,256, issued Sep. 24, 2002, to Amundson et al.; U.S. Pat. No. 6,574,510, to Von Arx et al., issued Jun. 3, 2003; and U.S. Pat. No. 6,614,406, issued Sep. 2, 2003, to Amundson et al., the disclosures of which are incorporated by reference. Unlike inductive telemetry, RF telemetry is long range, extending to about 20 or more feet from a patient without using repeaters. This range allows a patient free movement while the IMD is accessed. RF telemetry also offers a higher data transfer rate that can significantly shorten download time.
Although promising, the use of RF telemetry in IMDs potentially raises serious privacy and safety concerns. Sensitive information, such as patient-identifiable health information, exchanged between an IMD and the programmer or repeater should be safeguarded to protect against compromise. Prior to initiating a data exchange session, a clinician preferably first informs the patient and then proceeds only with the patient's knowledge. The short range of inductive telemetry can imply informed consent, but the longer range of RF telemetry can require additional precautions to secure proper patient/clinician authentication. Similarly, the wider transmission radius of RF telemetry could allow a third party to monitor or interfere with a data exchange session without authorization. Finally, a data exchange session could mistakenly be conducted with a wrong patient.
Recently enacted medical information privacy laws, including the Health Insurance Portability and Accountability Act (HIPAA) and the European Privacy Directive underscore the importance of safeguarding a patient's privacy and safety and require the protection of all patient-identifiable health information (PHI). Under HIPAA, PHI is defined as individually identifiable health information, including identifiable demographic and other information relating to the past, present or future physical or mental health or condition of an individual, or the provision or payment of health care to an individual that is created or received by a health care provider, health plan, employer or health care clearinghouse. Other types of sensitive information in addition to or in lieu of PHI could also be protectable.
The sweeping scope of medical information privacy laws, such as HIPAA, may affect patient privacy on IMDs with longer transmission ranges, such as provided through RF telemetry, and other unsecured data interfaces providing sensitive information exchange under conditions that could allow eavesdropping, interception or interference. Sensitive information should be encrypted prior to long range transmission. Currently available data authentication techniques for IMDs can satisfactorily safeguard sensitive information. These techniques generally require crypto keys, which are needed by both a sender and recipient to respectively encrypt and decrypt sensitive information transmitted during a data exchange session. Crypto keys can be used to authenticate commands, check data integrity and, optionally, encrypt sensitive information, including any PHI, during a data exchange session. Preferably, the crypto key is unique to each IMD. However, authentication can only provide adequate patient data security if the identification of the crypto key from the IMD to the programmer or repeater is also properly safeguarded.
Therefore, there is a need for a system and method to ensure patient privacy and safety by using secure methods for crypto key exchange. Preferably, such an approach will secure clinician/patient authentication prior to data exchange session initiation and will facilitate transacting a secure crypto key exchange between an IMD and a programmer, repeater or similar device.